1. Field of the Invention
The present invention relates to a twist-beam rear axle for motor vehicles. More particularly, the present invention relates to the use of aluminum extrusions to form a flexurally stiff but torsionally compliant cross strut and flexurally and torsionally stiff longitudinal arms.
2. Disclosure Information
A twist-beam rear axle of this kind for motor vehicles is known from German patent specification 44 41 971, wherein the cross strut is formed from a section which determines the position of the roll center and is in the form of an extruded aluminum channel section of which the open-bottom U-shaped cross-section is provided with closed chambers at the free ends of the sides of the section.
In this case the cross struts, after separation, or removal of a connecting piece, and bending the two sides apart outwards, form regions for the longitudinal arms which are formed by closure with corresponding shaped members.
The known twist-beam rear axle has the disadvantage that the U-shaped cross-section of the extruded aluminum channel section forming the cross strut has an undesirably high warping constant, which impairs the fatigue strength of the twist-beam rear axle. On alternating spring deflection, and thus twisting, of the cross strut the normal stresses set up in the transition region between the cross strut and the longitudinal arm are so high that cracks are formed after only a short time. In addition, the torsion constant which can be achieved is too small.
It is an object of the invention to provide a twist-beam rear axle of the kind referred to above capable of obtaining, by means of a correspondingly optimised cross-section of the cross strut in the form of an extruded aluminum channel section, as low a warping constant as possible together with high bending strength, particularly about the vertical axis, and increased torsional stiffness. Furthermore the particular position of the roll center also plays a significant part.